Power operated extrusion press for extruding a mass capable of abruptly releasing gas through a die

ABSTRACT

A power-operated extrusion press for extruding a mass capable of abruptly releasing a large volume of gas in which the mass is placed in a pressure pot and held in pressure engagement with a sealing surface on the die and pressed out of the pot through the die, is protected against damage due to such abrupt release of gas by providing in the path of pressure as generated by gas release a pressure surface dimensioned so that:

Kopp

[ 1 Sept. 5, I972 POWER OPERATED EXTRUSION PRESS FOR EXTRUDING A MASS CAPABLE OF ABRUPTLY RELEASING [57] ABSTRACT A power-operated extrusion press for extruding a mass GAS THROUGH A E capable of abruptly releasing a large volume of gas in [72] Inventor: Eugen Kopp, Stuttgart, G ny which the mass is placed in a pressure pot and held in [73] Assignee wemer & Weider", Stuttgam preissure endgageme? lwith a sailing zurtgacei on the die.

' 1 an presse out o t e pot roug e ie, is pro- Feuerbach Germany tected against'damage due to such abrupt release of [22] Filed: July 29, 1970 gas by providing in the path of pressure as generated [211 App No 59 087 by gas release a pressure surface dimensioned so that:

I 1' l pa [30] Foreign Applicafim Priority Data. wherein F is the area of the pressure surface;

1.969 Gel-mam,- "J 19 4 829-2 p the pressure with which the container is pressed 1 v against the sealing surface of the die and i [52] US. Cl ..425/376 51 Int. Cl. ..B29c 21 00 m the pressure of released gas acting in Opposition to l i 58 Field of Search.....l8/DIG. 4, DIG. 26,, DIG. 35, the dlrectwnnf the pressure p.. theymagmmde of pa 18/DIG. 45, 12 P, 16.7; 425/355, 376' being in excess of a selected pressuremagnitude p v presumed to act in the same direction as pressure p,,. [56] References Citedf By suitably selecting the area of pressure surface F UNITED STATES PATENTS v occurrence of an excessive and thus dangerous gas pressure p causes rapid lifting of the pot from the die 2,447,129 8/1948 ..18/l2 P against the action of sealing pressure pa thereby per 2,528,260 10/1950 Cademarton ..l8/12 P mining rapid dissipation of a dangerous build up in Primary E H A Kilb J the pressure pot. 4

xammery, r. v v Attomey-Hane, Baxley & Spiecens '3 Claims, 3 Drawing Figures 1 i I I H I i I i 7; r lil 1a; I i 5 fa" l l '7 t l /0 n W a E l a f l -64 J; u 1 t i 2i l l E a 1 if a i l 1!; r; El l 1 I i l ii\ i i l a y l 1 I r l 1 i i 2 l i l l 1 I/ I l l I y f 5 1 PATENTED SE? 5 1972 3.689.188

Ar VOM MQ M Arron/V675 PATENIEDSEP 5 I972 SHEET 2 BF 2 POWER OPERATED EXTRUSION PRESS FOR EXTRUDING A MASS CAPABLE OF ABRUPTLY RELEASING GAS THROUGH A DIE The invention relates to a hydraulically or otherwise operated press for extruding from a container through a die a plasticized and/or powderized mass capable of rapidly releasing a large volume of gas, such as an explosive mass.

BACKGROUND When and while a mass of the general kind above referred to is extruded a huge volume of gas may be suddenly released. Practical experience shows that in spite of all possible precautions detonation of an explosive mass during an extrusion operation cannot be always avoided. There are also various other types of masses that are not explosive in nature but nevertheless capable of abruptly releasing large volumes of gas due to more or less rapidly progressing decomposition processes.

As it is obvious, abrupt release of a huge volume of gas may result in disastrous damage to the press itself and is also dangerous for personnel operating the press or near it at the moment of the release of gas.

In power operated extrusion presses of the kind above referred to the mass to be extruded out through a die by means of a pressure ram is fed into a container commonly referred to as a pressure pot." This pot is held in pressure engagement with a sealing surface on the die by pressure means provided for the purpose on the press. Retraction means such as a lifting means also provided on the press serve to lift the pressure pot when a specific mass pressure 1 generated by the release of gas is in excess of a selected acceptable pressure p acting in opposition to the sealing pressure exerted upon the pressure pot.

The afore outlined problem is well known in the art. It may occur with all kinds of dies, that is, dies used for shaping the mass in the form of strands, discs, cubes, etc.

Evacuation of the pressure pot prior to the extrusion operation as commonly used does neither prevent the occurrence of the release of gas nor does it neutralize the effect of the gas pressure when it occurs.

Many attempts have been made to control or in other words, to render harmless an abruptly released huge volume of gas.

It has been proposed to provide frangible components on or in association with the pressure cylinder in which the ram or plunger of the press is reciprocating. These frangible components are designed to fracture when the pressure within the pressure cylinder exceeds the maximal acceptable operation pressure. When such excessive pressure occurs, for instance, due to detonation of an explosive mass contained in the pressure pot, the resulting release of gas forces the ram or plunger and the piston on which it is supported upwardly in the pressure cylinder thereby compressing the pressure fluid contained in the cylinder. An arrangement of this kind has been found to be unsatisfactory.

A true neutralization or at least reduction of the effect of an abrupt release of a large volume of gas can be obtained only by providing means permitting a rapid 0 "0115 consequences.

There are also known complex devices providing central cavities within the ram of the press and connecting such cavities through bores with the atmosphere. Pistons within the cavities are designed to be axially displaced in response to an excessive release of gas and thus to connect the cavities to the atmosphere via the bores. Safety devices of this kind are much to expensive in practice and also offer very little safety. The available passages for the'escape of the gas are bound to be too small to permit the required rapid dissipation of large volumes of gas. Moreover, all the disadvantages inherent in the use of movable components in extrusion presses are present such as the occurrence of leakage at the pistons resulting in contamination of the mass to be extruded. Moreover, the potentially dangerous explosive mass can penetrate into the ram itself via the bores.

It has further been proposed to provide means permitting an escape of the released gases at the area where such escape is most feasible, namely, directly between the die and the pressure pot. Basically, such means require that the pressure pot is lifted above the die in response to a beginning build-up of a dangerous pressure thereby permitting rapid escape of the gases. However, means using this principle as heretofore known, are very complicated in that they comprise a pressure piston included in the pressure conduit of the pressure cylinder of the press and biased by unilaterally acting spring pressure. The pressure piston is coupled with a control piston which, in turn, is connected to a pressure conduit for supplying pressure fluid to the lifting means for the pressure pot.

It is evident that such complicated means is not very practical; its operational reliability is bound to be uncertain, it is not capable of reacting rapidly enough and it is also economically not acceptable.

THE INVENTION It is a broad object of the invention to provide a novel and improved safety means for extrusion presses of the general kind above referred to which avoids the disadvantages of gas pressure release means as heretofore known and assures rapid dissipation of the large volume of gas as released by an explosion or rapid decomposition of the mass to be extruded.

A more specific object of the invention is to provide a novel and improved safety means of the general kind above referred to which utilizes existing components and assemblies of the press and which can thus be inexpensively manufactured and installed.

Another more specific object of the invention is to provide a novel and improved safety means which assures that the pressure pot is rapidly separated from the die in response to a dangerous pressure build-up and which avoids the use of movable and complex components.

SUMMARY OF THE INVENTION sealing pressure P, pressing the pressure pot against a sealing surface of the die in response to the generation of a gas pressure p, which is larger than a selected ac ceptable pressure p, that is: the area of surface F and the magnitude of pressure P, are selected so that:

As is now evident, the lifting means, that is, the means for retracting the pressure pot from the die as proposed according to the invention, are extremely simple and inexpensive as they merely require a suitable dimensioning of the pressure surface on the pressure pot.

According to a preferred embodiment of the invention, the pressure surface F 1 is formed by an outwardly tapered rim of the pressure pot at the end thereof facing the die. The pressure surface F, has the important advantage that the pressure surfacein conjunction with the die defines within the pressurev pot a space which due to the configuration of the pressure surface retains the so-called pressure cake or briquette on the die during the withdrawal stroke of the pressure ram. Retention of the pressure cake on the die is highly desirable as the cake constitutes, in effect, a seal for sealing the pressure pot against the die when the pressure pot is evacuated. I

According to another aspect of the invention, the cylinder of the extrusion press itself andalso hydraulic cylinders which are used as part of the pressure means for pressing the pressure pot against the die are protected against damage when the pressure pot is forcibly and rapidly lifted by a pressure build-up due to abrupt release of gas by frangible components on the cylinders. These components are designed to fracture in response to an excessive gas pressure thereby automatically rendering the cylinders inoperative for applying pressure to the pressure pot and to the mass to be extruded, respectively.

DETAILED DESCRIPTION OF THE INVENTION In the accompanying drawing a preferred embodirnent of the invention is shown by way of illustration and not by way of limitation.

In the drawing:

FIG. 1 is a diagrammatic elevational view, partly in section, of a hydraulically operated extrusion press including safety means according to the invention;

' FIG. 2 is a fragmentary sectional view of FIG. 1 showing the pressure pot and the die of the press on an enlarged scale; and

FIG. 3 is a sectional view of the die of the press with a press cake retained thereon.

Referring now to the figures more in detail, the exemplified extrusion press comprises a container or pressure pot 1 into which is fed the mass to be extruded. The mass such as an explosive mass may be in plasticized or pulverized condition, it may also be preliminarily shaped.

. the pressure pot to be lifted against the action of the Pressure pot 1 is pressed by a conventional pressure means shown as including hydraulic cylinders 3 against 'a die 5 fitted in a pressing table 15. The die may be or plunger 7 mounted on a piston 7a which is slideable in a press cylinder 14. The pressure ram is initially lowered in pot 1 until a pressure dome 6 supported by the ram abuts against the upper face of pot l. The pot is now evacuated via vacuum dome 6 in a conventional manner; a port 6a in the dome is indicated for the purpose. As it is evident, the space within pot 1 must be sealed vacuum-tight against die 5 and ram 7 of the press to effect evacuation of the pot.

When the pot is evacuated to the desired degree, ram 7 is further lowered toward die 5 so that mass present within the-pot, is extruded through die 5 and more specifically through insert 4 thereof. The ram is lowered until it is at a level such that only a rather thin layer of the mass remains in the'pot. This layer forms a pressure cake 16 as it is shown in FIG. 3, said cake acting as a seal for the pot. The ram is now returned to its starting position thereby completing the operational cycle.

As it is shown in the figures, the pressure pot has at its rim facing the die an outwardly slanted or tapered pressure surface 2. This surface constitutes part of the inner wall surface of the pot and faces in opposition to the pressure P, as produced by the afore referred to pressure means 3 pressing the pressure pot against the sealing surface 9 on the die. The pressure P, acts downwardly and in the axial direction of the pot thus opposing a pressure attempting to lift the pot that is, to retract the pot from its engagement with the die. Such lifting pressure is generated by release of gas as may be caused by a detonation of the mass within the pot or as previously indicated by a rapid decomposition of the mass. This pressure is designated as mass pressure p,. Pressure p, becomes excessive, that is, reaches a dangerous and hence not acceptable magnitude when it is larger than a selected normal or acceptable mass pressurep. 'As it is evident, the total area of surface 2 formed at the rim of the pot does not constitute the effective area of thissurface opposing the downward pressure P,, but only a projection of this area upon a horizontal plane as the surface 2 is slanted. The projected area, that is, the effective area of surface 2 is designated as pressure surface F Hence, the following equation applies:

where D is the diameter 11 of FIG. 2; and d is diameter.

8 in FIG. 2. In accordance with the invention, the area F, is dimensioned in accordance with the formula:

The actual relation between the normal or acceptable specific mass pressure force p per unit area and the increased or mass pressure force p, per unit area so as to obtain a suitably dimensioned pressure surface F must be calculated from case to case and is also affected by empirical factors. The pressure P, must be such that the mass within the pot, which is under high specific pressure at a normal extrusion operation, cannot creep out between the bottom rim of pot l and the die; the pressure required for this purpose can be calculated without difficulty. Theoretically, a pressure force p which is only very slightly larger than the selected reference pressure force p would be sufficient to obtain a suitable pressure surface F when inserted into the afore stated formula but in actual practice, the surface F, should be larger than the theoretically acceptable minimum size, the more so as an increase of the specific mass pressure force p within pot 1 above the theoretical magnitude of the pressure is generally acceptable. A suitable magnitude of pressure force p can be calculated, in practice, without difficulty on the basis of existing experience.

The slanted rim surface 2, which is contiguous to also slanted sealing surface 9, in conjunction with the top side of die 5 defines within the pot a space 17 which is diametrically enlarged with reference to the diameter of the remaining inner wall surface of the pot. This space safely retains pressure cake 16 on the die (see FIG. 3). As pointed out before, this cake is necessary to seal the pressure pot against the die when the latter is evacuated for the next extrusion cycle.

As it is now evident, generation of pressureforce p, acting upon the effective pressure surface F will cause a very rapid lifting of pot 1 thereby providing a wide escape passage for the gas permitting a rapid escape thereof.

The rapid lifting of pot I obviously requires that the hydraulic pressure fluid in cylinder spaces in the hydraulic cylinders 3 of the pressure means is displaced in an equally short period of time. To permit such rapid movement of the hydraulic fluid the end wall 12 of the cylinders is frangible. Similarly, rapid movement of ram 7 and its piston 7a in cylinder 14 are made possible by one or more frangible caps 18. Fracture of the frangible walls and caps permits a rapid escape of the hydraulic pressure fluid normally confined in spaces 10 and 13.

While the invention has been described in detail with respect to a certain now preferred example and embodiment of the invention, it will be understood by those skilled in the art, after understanding the invention, that various changes and modifications may be made without departing from the spirit and scope of the invention, and it is intended therefore, to cover all such changes and modifications in the appended claims.

What is claimed is:

1. In a power-operated extrusion press wherein a mass capable of abruptly releasing a large volume of gas is extruded from a container including a cylindrical space through adie and the container is held by a pressure means in sealing engagement with the die with a downward pressure force P and wherein the container is retracted from engagement with the die in response to an upward pressure force p acting in opposition to pressure force P and being greater than an upward pressure force p where pressure force p, is the pressure force generated by the abrupt release of gas and pressure force p is a selected reference pressure force, the improvement comprising retraction means including a pressure surface F formed on the inner container wall finin the ace erein, said ressure surface bei i sposl in tin patii of the press ure force p, upwardl? acting in the direction of the container axis and in opposition to the downward pressure force P and causing retraction of the container from the die in response to a pressure force p, upon surface F 'having an effective area such that:

said container having on its inner wall at the end of the container facing the top side of the die an outwardly slanted peripheral surface portion and the die having an outwardly slanted surface portion extending from the top side of the die facing said container and being movable into abutting engagement with the slanted surface portion on the inner container wall, the minimal slanted surface portions of the container wall when said slanted surface portions are in said abutting engagement, said exposed part on the inner container wall constituting said pressure surface F and defining in conjunction with the top side of the die within the container a spaced portion having a maximal diameter larger than the diameter of the remaining space in the container for forming in said space a compacted layer of the mass when said pressure means are operated for exerting compacting pressure upon mass fed into the container.

2. The extrusion press according to claim 1 wherein said pressure means and further pressure means for extruding the mass through the die each include frangible components arranged to fracture in response to the generation of said oppositely directed gas pressure P, which is above a predetermined value, fracturing of said components rendering both said pressure means inoperative for exerting sealing pressure upon the container and extrusion pressure upon the mass, respectively.

3. The extrusion press according to claim 1 wherein said pressure means include a frangible component arranged to fracture in response to a lifting of the container from the die with an upward pressure above a predetermined value, fracturing of said component rendering the pressure means inoperative for exerting sealing pressure upon the die. 

1. In a power-operated extrusion press wherein a mass capable of abruptly releasing a large volume of gas is extruded from a container including a cylindrical space through a die and the container is held by a pressure means in sealing engagement with the die with a downward pressure force Pa and wherein the container is retracted from engagement with the die in response to an upward pressure force p1 acting in opposition to pressure force Pa and being greater than an upward pressure force p where pressure force p1 is the pressure force generated by the abrupt release of gas and pressure force p is a selected reference pressure force, the improvement comprising retraction means including a pressure surface F1 formed on the inner container wall defining the space therein, said pressure surface being disposed in the path of the pressure force p1 upwardly acting in the direction of the container axis and in opposition to the downward pressure force Pa and causing retraction of the container from the die in response to a pressure force p1 upon surface F1 having an effective area such that: p1.F1>Pa said container having on its inner wall at the end of the container facing the top side of the die an outwardly slanted peripheral surface portion and the die having an outwardly slanted surface portion extending from the top side of the die facing said container and being movable into abutting engagement with the slanted surface portion on the inner container wall, the minimal diameter of the slanted surface portion on the container being smaller than the minimal diameter of the slanted surface portion on the die, said differences of the diameters leaving exposed a peripheral part of said slanted surface portions of the container wall when said slanted surface portions are in said abutting engagement, said exposed part on the inner container wall constituting said pressure surface F1 and defining in conjunction with the top side of the die within the container a spaced portion having a maximal diameter larger than the diameter of the remaining space in the container for forming in said space a compacted layer of the mass when said pressure means are operated for exerting compacting pressure upon mass fed into the container.
 2. The extrusion press according to claim 1 wherein said pressure means and further pressure means for extruding the mass through The die each include frangible components arranged to fracture in response to the generation of said oppositely directed gas pressure Pa which is above a predetermined value, fracturing of said components rendering both said pressure means inoperative for exerting sealing pressure upon the container and extrusion pressure upon the mass, respectively.
 3. The extrusion press according to claim 1 wherein said pressure means include a frangible component arranged to fracture in response to a lifting of the container from the die with an upward pressure above a predetermined value, fracturing of said component rendering the pressure means inoperative for exerting sealing pressure upon the die. 